This invention is related to a child seat sensing means in a motor vehicle, and more particularly to apparatus disabling the airbag system for a car seat supporting a child's seat.
Recent government regulations for child restraint's and airbag suppression necessitate a low cost integral load sensor.
A load sensor can be used with automobile onboard electronic logic to store seat belt forces for accident investigations, and for the development of load limiting devices to reduce injury to the vehicle occupants.
A load transducer can also be used to determine if the load is high enough to warrant the replacement of the seat belt. Visual inspection of the seat belt is the only means used by manufacturers today to replace the belt.
A load transducer can also be used with electronically controlled seat belt load limiters to control the maximum seat belt force a particular sized person should receive before the restraint system, such as an airbag system, is deployed or energized.
Typically, seat belts strapped around an adult have a small retraction force when the adult is buckled up. However, a properly secured child seat mounted on the same car seat will provide a relatively high tensile load upon the lap belt.
Some prior art devices related to these problems include: U.S. Pat. No. 5,996,421 issued Dec. 7, 1999, to Harald Snorre Husby for "Seat Belt Tension Sensor Employing Flexible Potentiometer"; U.S. Pat. No. 5,991,676 issued Nov. 23, 1999, to Robert Michael Podoloff and Ronald Anthony Vallette, Jr. for "Seat Occupant Sensing System"; U.S. Pat. No. 5,865,463 issued Feb. 2, 1999, to Gagnon et al. for "Airbag Deployment Controller"; U.S. Pat. No. 5,851,026 issued Dec. 22, 1998, to Aloyse Schoos and Michael White for "Method and Installation for Detecting Certain Parameters Concerning an Auxiliary Child Seat with a View to Controlling the Operation of the Airbags of a Vehicle"; U.S. Pat. No. 5,785,347 issued Jul. 28, 1998, to Adolph et al. for "Occupant Sensing and Crash Behavior System"; and U.S. Pat. No. 3,817,093 issued Jun. 18, 1974, to Charles W. Williams for "Seat Belt Webbing Tension Measuring Device".
Anticipated laws require that passenger side seat airbags be suppressed when a child seat is present.
The preferred embodiment of the invention comprises a seat belt transducer, which compensates for the tensile force applied by the belt to a properly fastened child seat. The seat belt tension information is sent to the electronic control module (ECM). The ECM then disables the airbag system if a child's seat is strapped on a car seat.
The preferred embodiment of the invention comprises a transducer having a transducer plate mounted and secured parallel to a steel structural plate. Both plates are connected to an anchor device attached to the vehicle frame. Both plates have a belt opening for receiving a belt loop. However, the belt openings are offset so that a light load on the seat belt is applied only to the transducer plate.
The transducer plate is elongated within its elastic limits under a tensile load. Thus an initial tensile load applied by the belt, such as caused by a strapped down child's seat, will be connected through the transducer plate to the anchor device.
Tension in the transducer plate is converted to an electrical signal by a strain gage. This reading is sent to the ECM, which determines from the tension on the seat belt whether or not the airbag system is to be inflated.
In the event of a high-speed accident, the transducer plate stretches until the belt-receiving openings in the two plates are aligned, at which time the primary belt load passes through the structural plate instead of the transducer plate. A strain gage is mounted on the transducer plate to transmit a signal that is proportional to the strain, to the ECM.
The transducer plate also has an integral web protector that prevents tearing of the seat belt. The wire to the strain gage is routed from the strain gage around the belt opening and up the belt webbing. The seat belt webbing protects the strain gage wire and presents a clean appearance.
Still further objects and advantages of the invention will become readily apparent to those skilled in the art to which the invention pertains, upon reference to the following detailed description.